III nitride single crystals have extraordinary utility as materials to create substrates for light-emitting diodes, electronic circuit elements, and semiconductor sensors.
To date, III nitride single crystals for such applications have been grown by vapor-phase techniques such as hydride vapor-phase epitaxy (HVPE) or metalorganic chemical vapor deposition (MOCVD)—for example, reference is made to Non-Patent Document 1—as well as by liquid-phase techniques such as high nitrogen pressure growth or the flux method—for example, reference is made to Patent Document 1 and Non-Patent Document 2.
With vapor-phase techniques such as HVPE and MOCVD, however, inasmuch as the source materials for the III nitride single crystals (that is, Group III elements and nitrogen) are transported in the gas phase, the source-material yield is on the order of an extremely low 1%.
On the other hand, with liquid-phase techniques such as high nitrogen pressure growth or the flux method, the fact that the amount of nitrogen that dissolves into a liquid phase is extremely low leads to extremely low III-nitride monocrystalline growth rates.
With regard to the growth of SiC single crystal, meanwhile, growing SiC single crystal at high crystallization speeds by stacking together a monocrystalline SiC substrate and a polycrystalline SiC plate, with a molten Si layer intervening, has been proposed—for example, reference is made to Patent Document 2. Nevertheless, in growing SiC single crystal, transporting carbon atoms in the solid phase is a challenge, whereas in growing III nitride single crystals, the difference is that transporting nitrogen atoms in the gas phase is a challenge.
Patent Document 1: Japanese Unexamined Pat. App. Pub. No. 2001-58900.
Patent Document 2: Japanese Unexamined Pat. App. Pub. No. 2002-47100.
Non-Patent Document 1: H. Morkoc, “Comprehensive Characterization of Hydride VPE Grown GaN Layers and Templates,” Materials Science and Engineering, R33, 2001, pp. 135-207.
Non-Patent Document 2: H. Yamane et al., “GaN Single Crystal Growth by the Flux Method,” Applied Physics, The Japan Society of Applied Physics, 2002, Vol. 71, No. 5, pp. 548-552.